Chapter 9.1, Problem 20E

In Exercises 9.15–9.22, hypothesis tests are proposed. For each hypothesis test,

1. a.      determine the null hypothesis.
2. b.      determine the alternative hypothesis.
3. c.       classify the hypothesis test as two tailed, left tailed, or right tailed.

9.20 Worker Fatigue. A study by M. Chen et al. titled “Heal Stress Evaluation and Worker Fatigue in a Steel Plant” (American Industrial Hygiene Association, Vol. 64, pp. 352–359) assessed fatigue in steel-plant workers due to heat stress. Among other things, the researchers monitored the heart rates of a random sample of 29 casting workers. A hypothesis test is to be conducted to decide whether the mean post-work heart rate of casting workers exceeds the normal resting heart rate of 72 beats per minute (bpm).